1) Field of the Invention
The present invention relates generally to hydraulic controls for a variable output hydraulic device such as a transmission or hydraulic flow system on a vehicle, and more specifically, to a simple circuit for inhibiting initial high speed or high volume operation of such a system upon start up of the vehicle.
2) Related Art
Utility vehicles such as skid steer loaders often include a hydraulically driven transmission having low speed and high speed operation. Valves on the transmission are electronically controlled to select speed, and a switch or other transmission speed select control at the operator console connected to the valve solenoid of one of the valves allows the operator to choose either the low speed or high speed range. In many systems, if the operator shuts down the vehicle with the select control in a high speed position, the high speed operation selection will carry over after the next start up unless the operator manually moves the select control.
It is often desirable to have vehicle operation after start up commence in the low speed range rather than the high speed range. Assuring that the low speed range is selected regardless of the position of the selection control can require complicated mechanical or electrical interlocks or interlock circuitry. Arrangements that only allow vehicle starting only if the low speed is manually selected can be complex and expensive and can be confusing to the operator.
Other hydraulic systems on the vehicle may have electrohydraulic valves or similar control devices for providing a variable hydraulic output. In many applications it is desirable to inhibit high flow or volume output upon vehicle start up.